jQuery Ajax Chain

The $.AjaxChain jQuery helper class allows to perform multiple synchronously chained Ajax calls; its optional settings make possible to filter data and pass it between succeeding calls, manage custom errors, create caching mechanisms and conditionally halt queue progression.

Documentation

Note: although being written in plain JavaScript, this library adopts the TypeScript interface definition standard to document its features.

Constructor

name	description
$.AjaxChain():JQueryAjaxChain	The $.ajaxChain helper class extends the JQueryPromise<T> object (http://api.jquery.com/Types/#Promise) with custom methods.

Public methods

name	chainable	description
enqueue(confObj: AjaxChainConfiguration | AjaxChainConfiguration[]):JQueryAjaxChain	yes	Enqueues one or more configuration objects for later processing.
dequeue():JQueryAjaxChain	yes	Sequentially and synchronously dequeues the configuration objects enqueued via enqueue() method in the order they were added, triggering the related Ajax calls.
clearQueue():JQueryAjaxChain	yes	Clears the currently queued configuration objects.
state():string	no	jQuery API Reference.
then<U>(doneFilter: (value?: T, ...values: any[]) => U | JQueryPromise<U>, failFilter?: (...reasons: any[]) => any, progressFilter?: (...progression: any[]) => any):JQueryPromise<U>	yes	jQuery API Reference.
done(doneCallback1?: JQueryPromiseCallback<T> | JQueryPromiseCallback<T>[], ...doneCallbackN: Array<JQueryPromiseCallback<T> | JQueryPromiseCallback<T>[]>):JQueryPromise<T>	yes	jQuery API Reference.
fail(failCallback1?: JQueryPromiseCallback<any> | JQueryPromiseCallback<any>[], ...failCallbacksN: Array<JQueryPromiseCallback<any> | JQueryPromiseCallback<any>[]>):JQueryPromise<T>	yes	jQuery API Reference.
always(alwaysCallback1?: JQueryPromiseCallback<any> | JQueryPromiseCallback<any>[], ...alwaysCallbacksN: Array<JQueryPromiseCallback<any> | JQueryPromiseCallback<any>[]>):JQueryPromise<T>	yes	jQuery API Reference.
progress(progressCallback1?: JQueryPromiseCallback<any> | JQueryPromiseCallback<any>[], ...progressCallbackN: Array<JQueryPromiseCallback<any> | JQueryPromiseCallback<any>[]>):JQueryPromise<T>	yes	jQuery API Reference.

Callback functions arguments

Note: differently from the original jQuery implementation, callbacks specified as arguments of then(), done(), fail(), always() methods get passed an array of responses: [response[,responseN, ...]]. Furthermore, callbacks specified as arguments of progress() method get passed an object structured as follows:

key	value
index:number	Dequeued Ajax call zero-based index
label:string	Dequeued Ajax call label, either user-defined or randomly generated
data:any	Dequeued Ajax call response

Configuration object

key	description
ajaxSettings:JQueryAjaxSettings	jQuery $.ajax method settings.
label?:string	Configuration object label (see progress() callback functions argument).
transform?:Function	Returning a truthy value allows to arbitrarily overwrite the next queued Ajax call 'data' property value specified in the original jQuery $.ajax method configuration object ('ajaxSettings'). See example #1.
appendToUrl?:Function	Returning a truthy value (String) allows to append string fragments to the next queued Ajax call 'url' property value specified in original jQuery $.ajax method configuration object ('ajaxSettings'); handy when dealing with semantic urls. See example #2.
hasErrors?:Function	Returning a truthy value determines any registered fail callback(s) to be called immediately, passing the former as an argument; the queue is then rejected. See example #3.
hasCache?:Function	Returning a truthy value allows to prevent the related Ajax call from being executed, passing the former as a parameter to any registered handler(s); useful to create caching mechanisms. See example #4.
hasHaltingCapabilities?:Function	Returning a truthy value prevents the queue from further progressing to the succeeding Ajax calls; the queue is then resolved. See example #5.
isSkippable?:Function	Returning a truthy value prevents the queue from being halted in case of $.Ajax error. See example #6.

Note: All functions specified as values of optional configuration object properties (marked with a question mark) are passed the dequeued Ajax call response as argument.

Examples

Typical setup

var ajaxChain = new $.AjaxChain();
ajaxChain.enqueue([configurationObject[,configurationObjectN, ... ]])
         .dequeue()
         .then(doneCallback, failCallback, progressCallback);

Common configuration patterns

<!-- The succeeding examples assume the following xml response: -->

<?xml version = "1.0"?>
<items>
    <item id="000001">
        <name>Item #1</name>
        <categoryId>1</categoryId>
    </item>
    <item id="000002">
        <name>Item #2</name>
        <categoryId>2</categoryId>
    </item>
    <item id="000003">
        <name>Item #3</name>
        <categoryId>3</categoryId>
    </item>
</items>

1. Dynamically passing data between succeeding Ajax calls:

var ajaxChain,
    configurationObj1,
    configurationObj2;
ajaxChain = new $.AjaxChain();
configurationObj1 = {
    ajaxSettings: {
        type: "GET",
        dataType: "xml",
        url: "/items"
   },
   transform: function(xmlResponse){
        var nextCallDataObj;
        if (xmlResponse) {
            nextCallDataObj = {
                id: $(xmlResponse).find('item')
                                  .first().attr('id')
            };                   
            return nextCallDataObj;               
        }                  
        return false;              
   }
};
// configuration object omitted for brevity
configurationObj2 = { . . . };
ajaxChain.enqueue([configurationObj1, configurationObj2])
         .dequeue()
         .then(doneCallback, failCallback, progressCallback);

2. Dynamically appending url fragments between succeeding Ajax calls:

var ajaxChain,
    configurationObj1,
    configurationObj2;
ajaxChain = new $.AjaxChain();
configurationObj1 = {
    ajaxSettings: {
        type: "GET",
        dataType: "xml",
        url: "/items"
    },
    appendToUrl: function(xmlResponse){
        var nextCallUrlFragment = "";
        if (xmlResponse) {
            nextCallUrlFragment = "/" + $(xmlResponse).find('item')
                                                      .first()
                                                      .attr('id');
        };                 
        return nextCallUrlFragment;               
    }               
};
// configuration object omitted for brevity
configurationObj2 = { . . . };
ajaxChain.enqueue([configurationObj1, configurationObj2])
         .dequeue()
         .then(doneCallback, failCallback, progressCallback);

3. Dynamically resolving queue upon custom errors:

var ajaxChain,
    configurationObj1,
    configurationObj2;
ajaxChain = new $.AjaxChain();
configurationObj1 = {
    ajaxSettings: {
        type: "GET",
        dataType: "xml",
        url: "/items"
    },
    hasErrors: function(xmlResponse){
        var $tempXmlResponse,
            categoryFilter = "1";
        $tempXmlResponse = $(xmlResponse);
        // check current Ajax call response for errors
        if ($tempXmlResponse.find("item").eq(0)
                            .find("categoryId")
                            .text()
                            .indexOf(categoryFilter) !== -1) {
            return "[Exception] forbidden category id: " + categoryFilter;
        }
        return false;         
   }
};
// configuration object omitted for brevity
configurationObj2 = { . . . };
ajaxChain.enqueue([configurationObj1, configurationObj2])
         .dequeue()
         .then(doneCallback, failCallback, progressCallback);

4. Creating caching mechanisms:

var ajaxChain,
    configurationObj1,
    configurationObj2;
ajaxChain = new $.AjaxChain();
configurationObj1 = {
    ajaxSettings: {
        type: "GET",
        dataType: "xml",
        url: "/items"
    },
    hasCache: function(xmlResponse){  
        // retrieve possible cached results
        if (itemsCollection.length) {
            return itemsCollection.toJSON();
        }
        return false;     
    }
};
// configuration object omitted for brevity
configurationObj2 = { . . . };
ajaxChain.enqueue([configurationObj1, configurationObj2])
         .dequeue()
         .then(doneCallback, failCallback, progressCallback);

5. Halting queue upon conditional logic:

var ajaxChain,
    configurationObj1,
    configurationObj2;
ajaxChain = new $.AjaxChain();
configurationObj1 = {
    ajaxSettings: {
        type: "GET",
        dataType: "xml",
        url: "/items"
    },
    hasHaltingCapabilities: function(xmlResponse){
        var $tempXmlResponse;
        $tempXmlResponse = $(xmlResponse);
        if ($tempXmlResponse.find("item").eq(0)
                            .find("categoryId")
                            .text().indexOf("1") !== -1) {
            return true;
        }
        return false;        
    }
};
// configuration object omitted for brevity
configurationObj2 = { . . . };
ajaxChain.enqueue([configurationObj1, configurationObj2])
         .dequeue()
         .then(doneCallback, failCallback, progressCallback);

6. Preventing a queue from being halted in case of $.Ajax error:

var ajaxChain,
    configurationObj1,
    configurationObj2;
ajaxChain = new $.AjaxChain();
configurationObj1 = {
    ajaxSettings: {
        type: "GET",
        dataType: "xml",
        url: "/items"
    },
    isSkippable: function(xmlResponse){
        return true;
    }
};
// configuration object omitted for brevity
configurationObj2 = { . . . };
ajaxChain.enqueue([configurationObj1, configurationObj2])
         .dequeue()
         .then(doneCallback, failCallback, progressCallback);

TypeScript

Visual Studio (NuGet)

1. Open the Package Manager Console
2. Install-Package jquery-ajax-chain.TypeScript.DefinitelyTyped

Node.js (TSD)

1. Open a shell in your project's scripts folder
2. npm install tsd -g
3. tsd install jquery-ajax-chain --save

Testing

Headless

1. Open a shell in the package root folder
2. npm install
3. bower install
4. grunt test:headless

Browser

1. Open a shell in the package root folder
2. npm install
3. bower install
4. grunt test:browser (--port option available, e.g.: grunt test:browser --port=8083)

Note: this project was packaged with grunt-init-jquery.